The present invention relates to a semiconductor device and, more particularly, to a technology effective if applied to the package of a large-scale integrated circuit of high integration.
In the prior art, the semiconductor chip is sealed up with a molding resin so that it may be protected. Several methods are used to mount leads in position on the semiconductor chip before the sealing.
For example, a lead frame having tabs at its center is used and mounted before the semiconductor chip is sealed. In this prior art, there is known a method of connecting electrode pads around the semiconductor chip with the corresponding inner leads through bonding wires.
The common problem among the semiconductor packages of the prior art is that the metal lead frame is cracked along the mold parting lines providing the exits of the lead lines.
Another problem is that the passages for moisture or contaminants in the atmosphere to steal along the metal lead wires from the outside into the semiconductor chip are relatively short.
Moreover, the surface mounting type package is seriously troubled by the so-called xe2x80x9creflow crackingxe2x80x9d problem that the moisture contained in the package is expanded by the heat of the solder reflow to crack the package.
Still another problem is that the bonding wires necessary for connecting the inner leads with the electrode pads of the semiconductor chip cannot be intersected partly because they are relatively long and partly because they are alternately assigned to input/output terminals.
In order to solve the above-specified problems, therefore, there has been proposed in Japanese Patent Laid-Open No. 241959/1986 (corresponding to E.P. Publication No. 0198194) a semiconductor device in which a plurality of inner leads are adhered to the circuit forming surface of a semiconductor chip through the semiconductor chip and insulating films by an adhesive, in which the inner leads and the semiconductor chip are electrically connected through bonding wires and in which common inner leads (or bus bar inner leads) are disposed in the vicinity of the longitudinal center line or the circuit forming surface of the semiconductor chip.
Also disclosed in Japanese Patent Laid-Open No. 167454/1985 or 218139/1986 (corresponding to U.S. Ser. No. 845,332) Is the package structure of the so-called xe2x80x9ctabless lead frame typexe2x80x9d, in which the tabs (i.e., the die pads) mounting the chip are eliminated to mount the chip on the insulating films adhered to the leads (i.e., Chip On Lead) and in which the bonding pads of the chip and the leading ends of the leads are connected through wires.
Also proposed in Japanese Patent Laid-Open No. 92556/1984 or 23613/1986 is the package structure in which the leads are adhered to the upper surface of the chip (i.e., Lead On Chip) by an adhesive and in which the bonding pads of the chip and the leading end portions of the leads are connected through wires.
According to the above-specified package structure arranged with the leads on the upper or lower surface of the chip, the heat and moisture resistances of the package can be improved because the leads in the package can be elongated. Thanks to the elimination of the tabs, moreover, the contact between the resin and the leads is improved to improve the reflow cracking resistance. As a result, even the large-sized chip can be packed in the package of the existing size. Moreover, this package structure is advantageous in reducing the wiring delay because it can shorten the bonding wires.
We have investigated the aforementioned semiconductor devices of the prior art and have found the following problems:
(1) In the semiconductor device of the prior art, the inner leads are adhered to the circuit forming surface of the semiconductor chip through the semiconductor chip and the insulating films by the adhesive. Because of the large stray capacity between the inner leads and the semiconductor chip the semiconductor device has a problem that the signal transmission rate is dropped by the large stray capacity to increase the electrical noises.
(2) Because of the large area of the insulating films, the amount of moisture absorbed is increased so that the absorbed moisture is gasified and expanded in the package during the reflow, thus causing a problem that the package cracking is established by the moisture expansion.
(3) Since the aforementioned insulating films are made of a resin of polyimide, the amount of absorbed moisture is increased so that the absorbed moisture is gasified and expanded in the package during the reflow, thus causing the problem or package cracking.
(4) Since the aforementioned adhesive is made of an acrylic resin, it is degraded by the pressure cracker test or the like, thus raising a problem that the reliability is dropped by the electrical leakage between the leads and the corrosions of the aluminum electrodes.
(5) Since the circuit forming surface of the semiconductor chip is not coated all over with the resin coating of polyimide for protections against alpha rays, there arises a problem that errors are caused by the alpha rays.
(6) The common inner leads (i.e., bus bar inner leads) are used as radiating plates, but the element having a large exothermic portion is not covered all over with the inner leads. There arises a problem that the radiation is insufficient in an element of 1 watt or higher.
(7) Since the insulating films made of the aforementioned resin of polyimide has a large area, there arises a problem that the semiconductor device is weak in the temperature cycle.
(8) The wire bonding is accomplished across the aforementioned inner leads (i.e., bus bar inner leads), thus raising a problem in poor productivity.
(9) The aforementioned adhesive layer is so soft that the wire bonding conditions are difficult to set, thus raising the problem of poor productivity.
(10) This problem of poor productivity is also caused by the poor workability for mounting the insulating films on the semiconductor chip.
(11) Since the semiconductor chip is insufficiently fixed by the portions of the inner leads, it is moved in the resin sealing (or molding) operation, thus raising a problem that the productivity is poor.
An object of the present invention is to provide a technique for improving the reliability of a semiconductor device.
An object of the present invention is to provide a technique for a semiconductor device to improve the signal transmission rate due to the stray capacity between the semiconductor chip and the leads and to reduce the electrical noises.
Another object of the present invention is to provide a technique for a semiconductor device to improve the radiating efficiency of the heat generated.
Another object of the present invention is to provide a technique for a semiconductor device to reduce the influences of the heat during the reflow.
Another object of the present invention is to provide a technique for a semiconductor device to reduce the influences of the heat in the temperature cycle.
Another object of the present invention is to provide a technique for a semiconductor device to prevent the molding defects from being caused.
Another object of the present invention is to provide a technique for a semiconductor device, which has a package structure arranged with leads on the upper or lower surface of the chip, to reduce the parasitic capacity to be established between the chip and the leads.
Another object of the present invention is to provide a technique for a semiconductor device to improve the productivity.
Another object of the present invention is to provide a technique to improve the moisture resistance.
The foregoing and other objects and novel features of the present invention will become apparent from the following description to be made with reference to the accompanying drawings.
Representatives of the invention to be disclosed herein will be briefly described in the following:
1. A semiconductor device of the type, in which common inner leads are adhered to the vicinity of the center line taken in the X- or Y-direction of the principal surface of a semiconductor chip through insulators for insulating the semiconductor chip electrically, in which a plurality of signal inner leads are adhered to the principal surface of the semiconductor chip through insulators for insulating the semiconductor chip electrically, and in which the inner leads, the common inner leads and the semiconductor chip are electrically connected through bonding wires and sealed up with a mold resin, wherein the improvement resides in that the gaps between the semiconductor chip at the outer lead side than the portions bonded to the insulators and said inner leads are wider than those from the portions bonded to the insulators.
2. A semiconductor device according to the foregoing item 1, wherein the area occupied by the insulators is at most one half of the area of the semiconductor chip.
3. A semiconductor device according to the foregoing item 1, wherein the area for bonding the insulators and the principal surface of the semiconductor chip is practically minimized.
4. A semiconductor device according to each of the foregoing items 1 to 3, wherein the insulators are molded of a resin containing a portion of the inner leads.
5. A semiconductor device according to each of the foregoing items to 1 to 4 wherein the material of the insulators satisfies at least two of the following conditions:
(1) The saturated moisture absorption is equal to or less than that of the sealing resin;
(2) The dielectric constant is 4.0 or less for 103 Hz at a temperature from the room temperature to 200xc2x0 C.;
(3) The Barcol hardness (GYZ J934-1) at 200xc2x0 C. is 20 or more;
(4) The amount of a soluble halogen element is 10 ppm or less in the case of the uranium and thorium contents of 1 ppb or less and in the case of extraction at 120xc2x0 C. for 100 hours;
(5) The contact between the semiconductor chip and the inner leads is excellent;
(6) The thermal expansion coefficient is 20xc3x9710xe2x88x926/xc2x0 C. or less; and
(7) The theremost resin has a glass transition temperature of 220xc2x0 C. or more.
6. A semiconductor device of the type, in which all of a plurality of inner leads are so arranged on the principal surface of a semiconductor chip as to float from the principal surface of the semiconductor chip, in which the semiconductor ship is adhered and fixed to the deenergized ones or the inner leads, and in which the remaining inner leads and the semiconductor chip are electrically connected through bonding wires and sealed up with a mold resin.
7. A semiconductor device of the tape, in which a plurality or inner leads are so arranged on the principal surface of a semiconductor chip as to flat from the principal surface of the semiconductor chip, in which the side of the semiconductor chip opposite to the principal surface is adhered and fixed through insulators by a portion of the inner leads, and in which the inner leads and the semiconductor chip are electrically connected through bonding wires and sealed up with a mold resin.
8. A semiconductor device of the type, in which a plurality of inner leads are adhered to the principal surface of a semiconductor chip through insulators for insulating the semiconductor chip electrically, and in which the inner leads and the semiconductor chip are electrically connected through bonding wires, wherein the improvement resides: in that radiating leads electrically insulated from the semiconductor chip have their one-side ends held on the principal surface of the semiconductor chip at the central portion of the longitudinal side of the package; and in that the other terminals of the radiating leads are extended to above the principal surface of the semiconductor chip outside the package.
9. A semiconductor device according to the foregoing item 8, wherein the other ends of the radiating leads are extended to below the side opposite to the principal surface of the semiconductor chip outside of the package.
10. A semiconductor device according to the foregoing item 8 or 9, wherein the one-side ends of the radiating leads are extended to above the exothermic portions of the principal surface of the semiconductor chip.
11. A semiconductor device of the type, in which a plurality of inner leads are adhered to the principal surface of a semiconductor chip through insulators for insulating the semiconductor chip electrically, and in which the inner leads and the semiconductor chip are electrically connected through bonding wires, wherein the improvement resides: in that one-side ends of radiating leads electrically insulated from the semiconductor chip are held on the central portion of the longitudinal side of the package and on the side opposite to the principal surface of the semiconductor chip; and in that the other ends of the radiating leads are extended to above the principal surface of the semiconductor chip outside of the package or to below the side opposite to the principal surface of the semiconductor chip outside of the package.
12. A semiconductor device according to any of the foregoing items 8 to 11, wherein the radiating leads are equipped at their outside with radiating plates.
13. A semiconductor device according to any of the foregoing items 6 to 12, wherein common inner leads are arranged in the vicinity of the X- or Y-directional center line of the principal surface of the semiconductor chip.
14. A semiconductor device according to any of the foregoing items 1 to 12, wherein the bonding wires are coated with insulators.
15. A semiconductor device according to any of the foregoing items 1 to 6 or 13, wherein the semiconductor chip has its principal surface arranged with bonding pads which do not intersect with the bonding wires arranged on the principal surface and the common inner leads.
16. A semiconductor device according to any of the foregoing items 1 to 15, wherein the mold resin material is a resin composite which is prepared by blending a thermoset resin with 70 wt. % or more of a substantially spherical inorganic filler having a particle size distribution of 0.1 to 100 microns, an average particle diameter of 5 to 20 microns and the maximum packing density of 0.8 or more.
17. A semiconductor device according to the foregoing item 16, wherein the mold resin material is composed mainly of at least one of a phenol-set type epoxy resin, a resol type phenol resin and a bismaleimide resin.
18. A semiconductor device according to the foregoing item 16 or 17, wherein the mold resin material is composed mainly of the resol type phenol resin or the bismaleimide resin as the thermoset resin, and wherein its molding has a bending strength of 3 kgf/mm2 or more at 215xc2x0 C.
19. A semiconductor device according to any of the foregoing items 16 to 18, wherein the mold resin material contains as its inorganic filler spherical molten silica having a particle size distribution of 0.1 to 100 microns, an average particle diameter of 5 to 20 microns and the maximum packing density of 0.8 or more.
20. A semiconductor device according to any of the foregoing items 16 to 19, wherein the mold resin material is blended as its inorganic filler with 67.5 vol % or more of substantially spherical molten silica having a particle size distribution of 0.1 or 100 microns, an average particle diameter of 5 to 20 microns and the maximum packing density of 0.8 or more, and wherein its molding has a linear expansion coefficient of 1.4xc3x9710xe2x88x925/xc2x0 C. or less.
21. A semiconductor device according to any of the foregoing items 16 to 20, wherein the mold resin material has an extract of pH 3 to 7, in case it is mixed with ion exchange water in an amount of ten times and extracted at 120xc2x0 C. for 100 hours, an electric conductivity of 200 xcexcS/cm or less, and extractions of halogen ions, ammonia ions and metal ions of 10 ppm or less.
22. A semiconductor device of the type, in which a plurality of inner leads are adhered to the principal surface of a semiconductor chip with an adhesive through insulators for insulating the semiconductor chip electrically, and in which the inner leads and the semiconductor chip are electrically connected through bonding wires, wherein the improvement resides in that the adhesive is blended as a filler with spherical fine particles which have a constant particle diameter and which are selected from a thermoplastic resin or thermoset resin having a softening temperature higher than the inorganic or adhering temperature.
23. A semiconductor device of the type, according to the foregoing items 1 to 22 in which a plurality of inner leads are either adhered to the principal surface of a semiconductor chip with an adhesive through insulators for insulating the semiconductor chip electrically or arranged in a state floating from the principal surface of the semiconductor chip, and in which the inner leads and the semiconductor chip are electrically connected through bonding wires, wherein the improvement resides: in that the semiconductor chip is coated with an alpha ray shielding polyimide film at all its circuit forming regions other than bonding pads; and in that the semiconductor chip is formed with an insulating film on its portion to which are adhered at least the leading ends of the inner leads or suspension leads.
24. A semiconductor device according to the foregoing item 23, wherein the insulators are made of a thermoset resin containing a printable inorganic filler.
25. A semiconductor device according to the foregoing item 23 or 24, wherein the area occupied by the insulators is at most one half of the chip area.
26. A semiconductor device according to any of the foregoing items 23 to 25, wherein the semiconductor chip is formed with a polyimide film at its side opposite to the principal surface.
27. A semiconductor device according to any of the foregoing items 23 to 26, wherein the insulators are formed highly accurately by a wafer process including the steps of: a solvent-peeling type dry film to a semiconductor wafer; exposing and developing the dry film in an ordinary manner; applying a pasty insulator and burying it with squeezee; heating to cure the film; and peeling the film.
28. A semiconductor device according to the foregoing item 26, wherein the wafer process further includes the step of forming the insulators by developing and exposing a solder resist dry film.
29. A semiconductor device of the type, in which a plurality of inner leads are adhered to the principal surface of a semiconductor chip with an adhesive through insulators for insulating the semiconductor chip electrically, and in which the inner leads and the semiconductor chip are electrically connected through bonding wires, wherein the improvement resides in that an insulating film is arranged on all or some of the inner leads opposed and closest to the semiconductor chip.
30. A semiconductor device of the type, in which a plurality of inner leads are adhered to the principal surface of a semiconductor chip with an adhesive through insulators for insulating the semiconductor chip electrically, and in which the inner leads and the semiconductor chip are electrically connected through bonding wires, wherein the improvement resides in that the semiconductor chip has its principal surface covered wholly or partially with a substance which is more flexible or fluid than the mold resin to cover some or all of the bonding wires while the outside being sealed up with a resin.
31. A semiconductor device of the type, in which a plurality of inner leads are adhered to the principal surface of a semiconductor chip with an adhesive through insulators for insulating the semiconductor chip electrically, and in which the inner leads and the semiconductor chip are electrically connected through bonding wires, wherein the improvement resides in that the semiconductor chip has its principal surface covered wholly or partially with a bonding resin which covers some or all the bonding wires while the outside being sealed up with the mold resin.
32. A semiconductor device according to the foregoing item 31, wherein the outer surface of the mold resin covering the side of the semiconductor chip other than the main surface is recessed to expose a portion of the semiconductor chip substantially to the outside.
33. A semiconductor device according to any of the foregoing items 30 to 32, wherein common inner leads are disposed in the vicinity of the X- or Y-directional center line of the principal surface of the semiconductor chip.
34. A semiconductor device of the type, in which a plurality of inner leads are adhered to the principal surface of a semiconductor chip with an adhesive through insulators for insulating the semiconductor chip electrically, and in which the inner leads and the semiconductor chip are electrically connected through bonding wires, wherein the improvement resides in that the semiconductor chip is formed with a recess or rise in its side other than the principal surface.
35. A semiconductor device of the type, in which a plurality of inner leads are adhered to the principal surface of a semiconductor chip with an adhesive through insulators for insulating the semiconductor chip electrically, and in which the inner leads and the semiconductor chip are electrically connected through bonding wires, wherein the improvement resides in that the semiconductor chip is formed with a plurality of grooves in its side other than the principal surface.
36. A semiconductor device of the type, in which a plurality of inner leads are adhered to the principal surface of a semiconductor chip with an adhesive through insulators for insulating the semiconductor chip electrically, and in which the inner leads and the semiconductor chip are electrically connected through bonding wires, wherein the improvement resides in that the semiconductor chip is formed with a recess, a rise or a plurality of grooves in its side other than the principal surface while being left with a silicon oxide film.
37. A semiconductor device of the type, in which a plurality of inner leads are adhered to the principal surface of a semiconductor chip with an adhesive through insulators for insulating the semiconductor chip electrically, and in which the inner leads and the semiconductor chip are electrically connected through bonding wires, wherein the improvement resides in that the distance from the portions of the inner leads contacting with the semiconductor chip to the outer wall of a package is made larger than the distance from the side of the semiconductor chip opposite to the principal surface to the outer wall of the package.
38. A semiconductor device according to any of the foregoing items 1 to 37, wherein the semiconductor chip is two in which the bonding pads to the inner leads are disposed in mirror symmetry, and wherein the inner leads and the bonding pads of the semiconductor chip are electrically connected across the inner leads at the side of the principal surface of the two semiconductor chips and are sealed up with a mold resin.
39. A semiconductor device according to any of the foregoing items 34 to 38, wherein common inner leads are arranged in the vicinity of the X- or Y-directional center line of the semiconductor chips.
40. A semiconductor device according to any of the foregoing items 1 to 39, wherein the surface opposed to a substrate mounting said semiconductor device is formed with at least one of radiating groove which has its two ends opened to the outside at the sides of the semiconductor device.
41. A semiconductor device according to the foregoing item 40, wherein the side of the semiconductor device opposite to the side formed with the radiating groove is formed with a second radiating groove which is extended in the same direction of the first-named radiating groove and which has its two ends opened to the outside of the sides of the semiconductor device.
42. A semiconductor device according to the foregoing item 41 or 42, wherein the mold resin in the bottom of the radiating grooves formed in the surface opposed to the substrate mounting the semiconductor device has a thickness of 0.3 mm or less.
43. A semiconductor device according to any of the foregoing items 40 to 42, wherein common inner leads are arranged in the vicinity of the X- or Y-directional center line of the principal surface of the semiconductor chip.
44. A semiconductor device according to any of the foregoing items 40 to 43, wherein the semiconductor devices are so packed in their mounting substrates that their radiating grooves merge into each other.
45. A semiconductor device wherein leads arranged in the upper or lower surface of a chip packed in a package are partially folded outward with respect to the upper or lower surface of the chip.
According to the means of the foregoing item 1, the inner leads are so stepped that the gaps between the semiconductor chip at the outer lead side than the portions bonded to the insulators and said inner leads are wider than those from the portions bonded to the insulators. The stray capacity between the semiconductor chip and the leads can be made lower than that of the prior art to improve the signal transmission rate and reduce the electrical noises.
According to the means of the foregoing item 2, the area of the principal surface of the semiconductor chip occupied by the insulators is at most one half of the area of the semiconductor chip so that the moisture absorption by the insulating films can be dropped to reduce the influences of the heat during the reflow and in the temperature cycle.
Since, moreover, the stray capacity between the semiconductor chip and the leads is lower than that of the prior art, it is possible to improve the signal transmission rate and to reduce the electrical noises.
According to the means of the foregoing item 3, the area for bonding the insulators and the principal surface of the semiconductor chip is practically minimized to minimize the moisture absorption by the insulating films. As a result, it is possible to reduce the influences of the heat during the reflow and in the temperature cycle. Since, moreover, the stray capacity between the semiconductor chip and the leads is lower than that of the prior art, it is possible to improve the signal transmission rate and to reduce the electrical noises.
According to the means of the foregoing item 4, the insulators on the principal surface of the semiconductor chip are made of the resin molding including a portion of the inner leads to sufficiently enlarge the distance between the semiconductor chip and the inner leads so that the stray capacity between the semiconductor chip and the leads is far lower than that of the prior art. As a result, it is possible to improve the signal transmission rate and to reduce the electrical noises.
Since, moreover, the molding resin is selected as a material having a good matching with the sealing resin, it is possible to prevent the peeling between the molding resin and the sealing resin (or mold resin). As a result, it is possible to reduce the leakage between the inner leads.
According to the means of the foregoing item 5, the optimum insulator can be selected by the semiconductor element.
According to the means of the foregoing item 6, the semiconductor chip is adhered and fixed to those of the inner leads, which are not energized, whereas the remaining inner leads are arranged apart (i.e., electrically insulated) therefrom on the principal surface of the semiconductor chip. Since no insulating film is use, the moisture resistance can be improved. Moreover, the step of adhering the insulating film is eliminated.
According to the means of the foregoing item 7, the plural inner leads are arranged apart (or electrically insulated) from principal surface of a semiconductor chip, and the side of the semiconductor chip opposite to the principal surface is adhered and fixed through insulators by a portion of the inner leads, and in which the inner leads and the semiconductor chip are electrically connected through bonding wires and sealed up with a mold resin. Since the inner leads are not adhered to the principal surface of the semiconductor chip, this principal surface can be prevented from being broken or damaged. Since, moreover, no insulating film is used on the principal surface of the semiconductor chip, it is possible to improve the moisture resistance.
According to the means of the foregoing item 8, radiating leads electrically insulated from the semiconductor chip have their one-side ends held at the central portion of the longitudinal side of the package, and the other terminals of the radiating leads are extended to above the principal surface of the semiconductor chip outside the package. As a result, it is possible to improve the radiating efficiency of the heat of the exothermic portions of the semiconductor chip.
According to the means of the foregoing item 9, the other ends of the radiating leads of the means of the item 9 are extended to below the side opposite to the principal surface of the semiconductor chip outside of the package. As a result, it is possible to improve the radiating efficiency of the heat of the exothermic portions of the semiconductor chip.
According to the means of the foregoing item 10, the one-side ends of the radiating leads of the means of the foregoing item 9 are extended to above the exothermic portions of the principal surface of the semiconductor chip. As a result, it is possible to improve the radiating efficiency of the heat of the exothermic portions of the semiconductor chip
According to the means of the foregoing item 11, one-side ends of radiating leads electrically insulated from the semiconductor chip of the means of the foregoing item 10 are held on the central portion of the longitudinal side of the package and on the side opposite to the principal surface of the semiconductor chip, and the other ends of the radiating leads are extended to above the principal surface of the semiconductor chip outside of the package or to below the side opposite to the principal surface of the semiconductor chip outside of the package. As a result, it is possible to improve the radiating efficiency of the heat of the exothermic portions of the semiconductor chip.
According to the means of the foregoing item 12, the radiating leads of the means of any of the foregoing items 8 to 11 are equipped at their outside with radiating plates. As a result, it is possible to further improve the radiating efficiency of the heat of the exothermic portions of the semiconductor chip.
According to the means of the foregoing item 13, common inner leads (i.e., bus bar inner leads) of the means of any of the foregoing items 1 to 12 are arranged in the vicinity of the X- or Y-directional center line of the principal surface of the semiconductor chip. As a result, the bonding wires of the reference voltage (VSS) or the power source voltage (VCC) in the semiconductor chip can be wired within a small area without any shorting. It is also possible to improve the workability of the wire bonding.
According to the means of the foregoing item 14, the bonding wires of the means of the foregoing item 13 are coated with insulators. As a result, the bonding wires for connecting the signal line inner leads and the semiconductor chip can be prevented from being shorted with the signal inner leads.
According to the means of the foregoing item 15, the semiconductor chip of the means of the foregoing item 14 has its principal surface arranged with bonding pads (i.e., external terminals) which do not intersect with the bonding wires arranged on the principal surface and the common inner leads (i.e., bus bar inner leads). As a result, the bonding wires for connecting the signal line inner leads and the semiconductor chip can be prevented from being shorted with the signal inner leads.
According to the means of the foregoing items 16 to 21;
(1) The sealing material using a filler the substantially spherical molten silica having a particle size distribution of 0.1 to 100 microns, an average diameter of 5 to 20 microns and the maximum packing density of 0.8 or more has a lower molten viscosity and a higher material fluidicity than the angular molten silica in current use. When in the molding operation, the gold (Au) wires or leads are neither deformed nor is flown away the semiconductor chip. It is also possible to pack the narrow gap of the package fully.
(2) Since the sealing material using the spherical molten silica is little influenced in its molten viscosity and fluidicity, it is possible to increase the loading thereby to reduce the thermal expansion of the material.
(3) An excellent reliability can be attained if the resol type phenol resin and polyimide resin used are highly pure.
(4) The sealing material using the highly pure resol type phenol resin and polyimide resin provides moldings of high heat resistance and excellent mechanical strength at a high temperature. As a result, it is possible to attain both a reflow resistance (to package cracking) in case the package absorbs moisture and a reliability in the moisture resistance and the resistance to thermal shocks after the reflow.
According to the means of the foregoing item 22, a filler of spherical fine particles having a constant particle diameter is blended in the adhesive of the means of each of the foregoing items 1 to 21. As a result, the gap between the semiconductor chip and the leads can be controlled to a constant value (equal to the filler diameter) so that the dispersion of the capacity between the semiconductor chip and the leads can be reduced.
According to the means of the foregoing item 23, the semiconductor chip of the means of each of the foregoing items 1 to 21 is coated with an alpha ray shielding polyimide film at all its circuit forming region other than bonding pads, and the semiconductor chip is formed with an insulating film on its portions to which are adhered at least the leading ends of the inner leads or suspension leads. As a result, the whole circuit forming region can be shielded from the alpha rays by the alpha ray shielding polyimide film, and the semiconductor chip can be adhered and fixed by the insulating film.
Since, moreover, the insulating film is formed on the semiconductor chip at only the portions to which are adhered at least the leading ends of the inner leads and the suspension leads, it is possible to reduce the stray capacity between the semiconductor chip and the inner leads.
Incidentally, the wafer is not warped even if the thick insulators are formed by the wafer process but partially.
According to the means of the foregoing item 24, the insulating films of the means of the foregoing item 23 are made of a thermoset resin containing a printable inorganic filler. As a result, the insulating films can be made highly accurate in the wafer process.
According to the means of the foregoing item 25, the area occupied by the insulating films of the foregoing item 23 or 24 is at most one half of the chip area. As a result, the moisture absorption by the insulating films can be dropped to reduce the influences of the heat during the reflow and the in the temperature cycle.
Since, moreover, the stray capacity between the semiconductor chip and leads can be made smaller than that of the prior art, it is possible to improve the signal transmission rate and to reduce the electrical noises.
According to the means of the foregoing item 26, the semiconductor chip of the means of each of the foregoing items 22 to 24 is formed with a polyimide film at its side opposite to the principal surface. As a result, it is possible to prevent the cracking from being caused by the heat of the reflow.
According to the means of the foregoing item 27, the insulators of means of each of the foregoing items 23 to 26 are formed highly accurately by a wafer process including the steps of: a solvent-peeling type dry film to a semiconductor wafer; exposing and developing the dry film in an ordinary manner; applying a pasty insulator and burying it with squeezee; heating to cure the film; and peeling the film. Thus, the insulators can be formed highly accurately by the batch process to improve the productivity.
According to the means of the foregoing item 28, the insulators of the means of the foregoing item 26 are formed by developing and exposing a solder resist dry film. As a result, the productivity can be improved.
According to the means of the foregoing item 29, the insulating film is formed in a lead frame state on all or some of the inner leads opposed and closed to the semiconductor chip. As a result, the insulating film between the semiconductor chip and the inner leads of the means of the foregoing item 2 or 3 can be easily provided in an improved productivity.
According to the means of the foregoing item 30, the semiconductor chip has its principal surface covered wholly or partially with a substance which is more flexible or fluid than the sealing resin (or mold resin) to cover some or all of the bonding wires while the outside being sealed up with a resin. As a result, the mold resin can be kept away from direct contact with the bonding wires to prevent the bonding wires from being repeatedly deformed by the relative deformations between the semiconductor chip and the resin in the temperature cycle and accordingly from being broken due to fatigue.
According to the means of the foregoing item 31, the semiconductor chip has its principal surface covered wholly or partially with a bonding resin which covers some or all the bonding wires while the outside being sealed up with the mold resin. As a result, the mold resin can be kept away from direct contact with the bonding wires to prevent the bonding wires from being repeatedly deformed by the relative deformations between the semiconductor chip and the resin in the temperature cycle and accordingly from being broken due to fatigue.
According to the means of the foregoing item 32, the outer surface of the mold resin covering the side of the semiconductor chip of the means of the foregoing item 31 other than the main surface is recessed to expose a portion of the semiconductor chip substantially to the outside. The resin cracking during the reflow soldering operation can be prevented with neither poor moisture resistance of the bonding pads nor wire disconnection in the temperature cycle.
Here, the word xe2x80x9csubstantiallyxe2x80x9d imagines that there exists either such a thin cover film of resin as will e inevitably formed on the surface of a semiconductor chip during the fabrication process or such a thin resin layer as will be broken in case a steam pressure is built up in the package.
According to the means of the foregoing item 33, the common inner leads (or bus bar inner leads) of the means of each of the foregoing items 30 to 32 are disposed in the vicinity of the X- or Y-directional center line of the principal surface of the semiconductor chip. As a result, the bonding wires of the reference voltage (VSS) or the power source voltage (VCC) in the semiconductor chip can be wired within a small area without any shorting. It is also possible to improve the workability of the wire bonding.
According to the means of the foregoing item 34, the semiconductor chip is formed with a recess or rise in its side other than the principal surface. As a result, the mold resin can be restricted by the semiconductor chip to reduce the stress which is to be generated in the mold resin portion of the corners of the non-circuit surface of the semiconductor chip to be subjected to the reflow cracking, so that this reflow cracking can be prevented.
According to the means of the foregoing item 35, the semiconductor chip is formed with a plurality of grooves in its non-circuit surface. As a result, the mold resin can be restricted by the semiconductor chip to reduce the stress which is to be generated in the mold resin portion of the corners of the non-circuit surface of the semiconductor chip to be subjected to the reflow cracking, so that this reflow cracking can be prevented.
According to the means of the foregoing item 36, the semiconductor chip is formed with a recess, a rise or a plurality of grooves in its side other than the principal surface while being left with a silicon oxide (SiO2) film. Since the adhesion between the silicon oxide (SiO2) film and the mold resin is strong, it is possible to prevent the peeling of the mold resin from the side of the semiconductor chip opposite to the circuit forming surface. Thanks to the recess or rise or the plural grooves, moreover, it is possible to reduce the stress which is generated in the mold resin portion of the corner of the non-circuit side of the semiconductor chip by the mold resin so that the reflow cracking can be prevented.
According to the means of the foregoing item 37, the distance from the portions of the inner leads contacting with the semiconductor chip to the outer wall of a package is made larger than the distance from the side of the semiconductor chip opposite to the principal surface to the outer wall of the package. As a result, the average flow speeds of the resin through the individual passages can be equalized to prevent the formation of voids and bending and shortage of packing of the bonding wires. Since, moreover, the resistances to the resin flows in the individual passages are equalized, the semiconductor chip and the leads can be prevented from changing to realize the molding of a highly reliable package.
According to the means of the foregoing item 38, the semiconductor chip is two in which the bonding pads to the inner leads are disposed in mirror symmetry, and wherein the inner leads and the bonding pads of the semiconductor chip are electrically connected across the inner leads at the side of the principal surface of the two semiconductor chips and are sealed up with a mold resin. As a result, it is possible to package the element having the twice capacity without changing the external shape.
According to the means of the foregoing item 39, the common inner leads (or bus bar inner leads) are arranged in the vicinity of the X- or Y-directional center line of the semiconductor chips of the means of each of the foregoing items 34 to 38. As a result, the bonding wires of the reference voltage (VSS) or the power source voltage (VCC) in the semiconductor chip can be wired within a small area without any shorting. It is also possible to improve the workability of the wire bonding.
According to the means of any of the foregoing items 40 to 42, the heat transfer surface area of the resin-sealed type semiconductor device can be enlarged to drop the heat resistance of the semiconductor device.
According to the means of the foregoing item 44, the semiconductor devices of the means of each of the foregoing items 40 to 43 are so packed in their mounting substrates that their radiating grooves merge into each other. The cooling craft can be established in the direction of the radiating grooves and the second radiating grooves to cool the individual semiconductor devices efficiently.
According to the means of the foregoing item 45, the leads are partially folded outward with respect to the upper (or lower) side of the chip so that the distance between the chip and leads can be enlarged to reduce the aforementioned parasitic capacity.